Aircraft Drag Reduction System And Internally Cooled Motor System And Aircraft Using Same

ABSTRACT

An aircraft propulsion system with a drag reduction portion adapted to reduce skin friction on at least a portion of the external surface of an aircraft. The drag reduction portion may include an inlet to ingest airflow. The aircraft may also have an internally cooled electric motor adapted for use in an aerial vehicle. The motor may have its stator towards the center and have an external rotor. The rotor structure may be air cooled and may be a complex structure with an internal lattice adapted for airflow. The stator structure may be liquid cooled and may be a complex structure with an internal lattice adapted for liquid to flow through. A fluid pump may pump a liquid coolant through non-rotating portions of the motor stator and then through heat exchangers cooled in part by air which has flowed through the rotating portions of the motor rotor. The drag reduction portion and the cooled electric motor portion may share the same inlet.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to U.S. Provisional Patent ApplicationNo. 62/643,763 to Bevirt et al., filed Mar. 16, 2018, which is herebyincorporated by reference in its entirety. This application claimspriority to U.S. Provisional Patent Application No. 62/694,910 to Bevirtet al., filed Jul. 6, 2018, which is hereby incorporated by reference inits entirety.

FIELD OF THE INVENTION

This invention relates to the aviation field, namely an aircraftpropulsion system used on aerial vehicles.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a sketch of a propulsion system according to some embodimentsof the present invention.

FIG. 1B is a sketch of a propulsion system according to some embodimentsof the present invention.

FIG. 2A is a vertical take-off and landing aircraft in a take-offconfiguration according to some embodiments of the present invention.

FIG. 2B is a vertical take-off and landing aircraft in a forward flightconfiguration according to some embodiments of the present invention.

FIG. 3A is a partial cutaway view of a nacelle and rotor according tosome embodiments of the present invention.

FIG. 3B is a partial cutaway view of a nacelle and rotor according tosome embodiments of the present invention.

FIG. 3C is a partial rear view of a nacelle according to someembodiments of the present invention.

FIG. 3D is a partial rear view of a nacelle according to someembodiments of the present invention.

FIG. 4A is a shaded partial view of a nacelle and rotor according tosome embodiments of the present invention.

FIG. 4B is a view of a nacelle and rotor according to some embodimentsof the present invention.

FIG. 4C is a view of the interior of a nacelle according to someembodiments of the present invention.

FIG. 5A is a shaded view of a nacelle and rotor according to someembodiments of the present invention.

FIG. 5B is a shaded view of a nacelle and rotor according to someembodiments of the present invention.

FIG. 6A is a shaded view of a rotor and a nacelle with bypass accordingto some embodiments of the present invention.

FIG. 6B is a view of a rotor and a nacelle with bypass according to someembodiments of the present invention.

FIG. 6C is a partial cutaway view of a rotor and a nacelle with bypassaccording to some embodiments of the present invention.

FIG. 7A is a shaded view of a rotor and a nacelle with bypass accordingto some embodiments of the present invention.

FIG. 7B is a view of a rotor and a nacelle with bypass according to someembodiments of the present invention.

FIG. 8 is a view of a rotor and propeller hub according some embodimentsof the present invention.

FIG. 9A is a partial cutaway view of a motor with liquid coolingaccording to some embodiments of the present invention.

FIG. 9B is a partial cutaway view of a motor with liquid coolingaccording to some embodiments of the present invention.

FIG. 9C is a partial cutaway view of a motor with liquid cooling andassociated heat exchangers according to some embodiments of the presentinvention.

FIG. 10A is a photograph of a rotor structure adapted for internalcooling according to some embodiments of the present invention.

FIG. 10B is a photograph of a rotor structure adapted for internalcooling according to some embodiments of the present invention.

FIG. 10C is a side cutaway view of a rotor structure adapted forinternal cooling according to some embodiments of the present invention.

FIG. 10D is a top partial view of a rotor structure adapted for internalcooling according to some embodiments of the present invention.

FIGS. 11 is view of the cooling subsubystem flow paths according to someembodiments of the present invention.

FIG. 12 is a representational view of a bypass mechanism according tosome embodiments of the present invention.

FIG. 13 is a partial cross-sectional side view of a diffuser accordingto some embodiments of the present invention.

FIG. 14 presents representational views of flow paths according to someembodiments of the present invention.

FIG. 15A presents representation views of flow paths using a segmentedfan according to some embodiments of the present invention.

FIG. 15B is a representational view of flow paths using a partitioneddiffuser routing to a segmented fan according to some embodiments of thepresent invention.

FIG. 15C is a representational view of flow paths using a partitioneddiffuser according to some embodiments of the present invention.

FIG. 16A illustrates velocity distributions through a partitioneddiffuse according to some embodiments of the present invention.

FIG. 16B illustrates pressure distributions through a partitioneddiffuse according to some embodiments of the present invention.

FIG. 17A is a view of suction velocity at 0% suction velocity fraction.

FIG. 17B is a view of turbulent intensity at 0% suction velocityfraction.

FIG. 18A is a view of suction velocity at 10% suction velocity fraction.

FIG. 18B is a view of turbulent intensity at 10% suction velocityfraction.

FIG. 19A is a view of suction velocity at 20% suction velocity fraction.

FIG. 19B is a view of turbulent intensity at 20% suction velocityfraction.

FIG. 20 is a graph of energy loss vs. volume flow rate ratio accordingto some embodiments of the present invention.

SUMMARY

An aircraft propulsion system with a drag reduction portion adapted toreduce skin friction on at least a portion of the external surface of anaircraft. The drag reduction portion may include an inlet to ingestairflow. The aircraft may also have an internally cooled electric motoradapted for use in an aerial vehicle. The motor may have its statortowards the center and have an external rotor. The rotor structure maybe air cooled and may be a complex structure with an internal latticeadapted for airflow. The stator structure may be liquid cooled and maybe a complex structure with an internal lattice adapted for liquid toflow through. A fluid pump may pump a liquid coolant throughnon-rotating portions of the motor stator and then through heatexchangers cooled in part by air which has flowed through the rotatingportions of the motor rotor. The drag reduction portion and the cooledelectric motor portion may share the same inlet.

DETAILED DESCRIPTION

An aircraft propulsion system which can reduce drag on the rotornacelles, and on the aircraft as a whole. A drag reduction portion mayinclude ingesting air into the nacelle rearward of the rotor. Theingestion of air may thin or eliminate the turbulent boundary layerrearward of the ingested air inlet. The ingested air may also be used ina thermal management subsystem to aid in cooling of an electric motorused to power the aircraft. The thermal management subsystem may includeheat exchange from a cooling liquid internal to the motor to the flowingair ingested from the air inlet. In some aspects, the ingested air isused solely for drag reduction. In some aspects, the ingested air isused both to reduce drag and to cool a motor of the aircraft.

In some aspects, the ingested air is used to reduce drag on theaircraft, and the ingested airflow is used to drive a fan coupled to aliquid pump which drives coolant through the motor, eliminating orreducing the need for electrical power to drive the thermal managementof the motor. In some aspects, the ingested air may split into separateairflow paths, with a portion of the inletted air routed through thethermal management subsystem, and then routing through heat exchangersto cool the liquid used to cool the motor. This same air routed throughthe heat exchangers may then also drive a fan coupled the liquid pump,thus providing both convective cooling and driving the liquid flow inthe cooling system of the motor. Another portion of the ingested air maybypass the motor cooling system. The use of the bypass allows for anincrease in the volume of ingested air, which may allow for tuning ofthe amount of ingested air to reduce drag on the aircraft.

As shown in FIGS. 1A-1B, the aircraft propulsion system 100 includes: arotor 101, a nacelle 102 including a drag reduction portion, a drivemechanism 103 coupled to the rotor and the nacelle, and a thermalmanagement subsystem 104 in thermal communication with the drivemechanism and the air surrounding the system. The rotor includes a setof blades 105 coupled to a hub 106 and defines a cowling 107. Thenacelle 102 defines an outer surface 108 and a lumen 109, and the dragreduction portion includes an inlet 110 and an outlet 111, and caninclude a diffuser 112. The drive mechanism includes a rotary portion122 rigidly coupled to the hub, and a fixed portion coupled to thenacelle. The thermal management subsystem 104 includes a liquid coolingmechanism 123 and a heat exchanger 121 (e.g., a radiator), and caninclude a flow actuator 113.

The system 100 can optionally include: a tilt mechanism 120 housed atleast partially in the lumen of the nacelle, a power supply 114, and anyother suitable components. The system 100 can function to reduce skinfriction on at least a portion of the external surface of an aircraft.The system can manipulate airflow (e.g., external airflow, internalairflow, etc.) to convectively cool system components. The system canadditionally or alternatively function to: ingest the boundary layerformed on the aircraft surface (e.g., at a location between a rotor andnacelle of the aircraft propulsion system); and perform any othersuitable function.

The aircraft propulsion system can be used in conjunction with arotorcraft. The rotorcraft is preferably a tiltrotor aircraft with aplurality of aircraft propulsion systems (e.g., rotor assemblies, rotorsystems, etc.), operable between a forward arrangement and a hoverarrangement. However, the rotorcraft can alternatively be a fixed wingaircraft with one or more rotor assemblies, a helicopter with one ormore rotor assemblies (e.g., wherein at least one rotor assembly oraircraft propulsion system is oriented substantially axially to providehorizontal thrust), and/or any other suitable rotorcraft or vehiclepropelled by rotors. The rotorcraft preferably includes an all-electricpowertrain (e.g., battery powered electric motors) to drive the one ormore rotor assemblies, but can additionally or alternatively include ahybrid powertrain (e.g., a gaselectric hybrid including aninternal-combustion generator), an internal-combustion powertrain (e.g.,including a gas-turbine engine, a turboprop engine, etc.), and any othersuitable powertrain.

The term “rotor” as utilized herein, in relation to the aircraftpropulsion system or otherwise, can refer to a rotor, a propeller,and/or any other suitable rotary aerodynamic actuator. While a rotor canrefer to a rotary aerodynamic actuator that makes use of an articulatedor semi-rigid hub (e.g., wherein the connection of the blades to the hubcan be articulated, flexible, rigid, and/or otherwise connected), and apropeller can refer to a rotary aerodynamic actuator that makes use of arigid hub (e.g., wherein the connection of the blades to the hub can bearticulated, flexible, rigid, and/or otherwise connected), no suchdistinction is explicit or implied when used herein, and the usage of“rotor” can refer to either configuration, and any other suitableconfiguration of articulated or rigid blades, and/or any other suitableconfiguration of blade connections to a central member or hub. Likewise,the usage of “propeller” can refer to either configuration, and anyother suitable configuration of articulated or rigid blades, and/or anyother suitable configuration of blade connections to a central member orhub. Accordingly, the tiltrotor aircraft can be referred to as atilt-propeller aircraft, a tilt-prop aircraft, and/or otherwise suitablyreferred to or described.

As shown in FIGS. 1A and 1B, the aircraft propulsion system 100includes: a rotor, a nacelle, a drive mechanism coupled to the rotor andthe nacelle, and a thermal management subsystem in thermal communicationwith the drive mechanism and the air surrounding the system. The rotorincludes a set of blades coupled to a hub. The nacelle defines an outersurface, a lumen, an inlet, a diffuser, and an outlet. In some aspects,the nacelle may have a first outlet for air which has travelled throughthe thermal management subsystem, and a second outlet for air which hasbypassed the thermal management subsystem. The drive mechanism includesa rotary portion rigidly coupled to the hub, and a fixed portion coupledto the nacelle. The thermal management subsystem includes a liquidcooling mechanism and a heat exchanger (e.g., a radiator), and caninclude a flow actuator.

The system 100 can optionally include: a tilt mechanism housed at leastpartially in the lumen of the nacelle, a power supply, and any othersuitable components. The rotor functions to rotate in a fluid under thepower of the drive mechanism in order to provide thrust (e.g., to anattached aircraft). The rotor includes a set of blades coupled to a hub,and a cowling, or spinner, that at least partially encloses the hub. Therotor can optionally include any suitable components for supportingand/or controlling surfaces of the rotor (e.g., linkages and/oractuators for varying blade pitch, structural elements for retaining theset of blades and/or hub, etc.).

The set of blades functions to transfer the rotational momentum of therotor to the fluid, resulting in at least a portion of the fluid havingaxial momentum (e.g., to provide thrust). The rotor can have anysuitable number of blades; the rotor preferably has five blades, but canalternatively have three blades, four blades, six blades, and any othersuitable number of blades. The blades can be rigidly fixed to a hub,fixed to a hub and include variable pitch capability (e.g., by way of asuitable variable pitch linkage, cyclic pitch control, etc.), and/orconnected to a hub or rotor head by one or more hinges (e.g., a draghinge, a flap hinge, etc.) to enable blades to lead, lag, and/or flaprelative to the hub or rotor head during rotation of the rotor underaerodynamic loading. However, the blades can be otherwise suitablycoupled to one another and/or otherwise suitably mechanically linked toform at least a portion of the rotor. In a specific example, the rotorincludes five variable-pitch blades; in alternative examples, the rotorcan have any suitable number of blades having variable- or fixed-pitch.

The rotor blades are preferably unconstrained at the blade tips (e.g.,by any sort of physical structure), but the rotor can additionally oralternatively include a fairing that encloses the blade tips (e.g., suchas the duct of a ducted fan). In such variations, the fairing canfunction to dampen the acoustic signature components (e.g., acousticwaves) that originate from the blade tips during rotation. However, therotor blades can additionally or alternatively be constrained orunconstrained in any suitable manner.

The hub functions to mutually couple the set of blades and provide aregion at which the rotor couples to the drive mechanism and receivesrotary power (e.g., shaft power) therefrom. In variations, the hub candefine at least part of the rotary portion of the drive mechanism (e.g.,the rotor of an electric motor including a rotor and a stator, a part ofthe rotor of the electric motor, etc.). In further variations, the hubcan directly or indirectly couple to an output shaft of the drivemechanism.

The cowling functions to define the foremost point of contact of therotor with the external fluid (e.g., surrounding air), the surface uponwhich a boundary layer forms during aircraft motion, and the wettedsurface of the rotor aside from that of the set of blades. The cowlingalso functions to define an internal lumen to house all or part ofelements of the propulsion system (e.g., the drive mechanism, thethermal management subsystem, the hub, etc.).

The cowling is preferably shaped to minimize drag. In variations, thecowling rotates with the rotor relative to the nacelle and is separatedfrom the nacelle by a gap. The gap can define at least a portion of theinlet to the nacelle (e.g., an annular inlet, a segmented partialannulus, etc.). In alternative variations, the cowling and/or portionsthereof can remain static relative to the nacelle (e.g., wherein thecowling defines a slot through which the set of blades rotates) duringrotor operation. The diameter of the cowling in the forward-projecteddirection is preferably less than the diameter of the foremost point ofthe nacelle (e.g., the point of the nacelle closest to the cowling) inthe forward-projected direction; however, the diameter of the cowlingcan alternatively be greater than the diameter of the foremost point ofthe nacelle in the forward-projected direction, substantially equal tothe diameter of the foremost point of the nacelle in theforward-projected direction, or otherwise suitably sized in variationsof the aircraft propulsion system.

The nacelle functions to house components of the aircraft propulsionsystem, and to define the outer surface (e.g., wetted surface, externalsurface) of the portions of the aircraft propulsion system downstreamfrom the rotor. The nacelle can also function to ingest an external flowand internally decelerate the flow (e.g., via a diffuser) beforeegesting the flow (e.g., via an outlet). The nacelle defines an outersurface and a lumen and can include a drag reduction portion, whereinthe drag reduction portion can define an inlet, a diffuser, and/or anoutlet. The nacelle should be understood to include any structuralportion of the airframe (e.g., the nose, the wing, the tail section,etc.) arranged aft of and structurally supporting the drive mechanismand the rotor, and any other suitable components of the aircraftpropulsion system.

In variations, the nacelle is a distinct structural member from the wingand/or tail section to which the nacelle is attached (e.g., rigidlymounted, rotatably coupled via a tilt mechanism, etc.). In suchvariations, the nacelle is preferably not configured as a lifting bodybut can additionally or alternatively be configured to provide at leastsome lift to the aircraft during flight. In alternative variations, thenacelle can be integrated with the wing and/or tail section to which thenacelle is attached. In such variations, the nacelle can define alifting and/or control surface (e.g., act as a part of the wing and/ortail section). However, the nacelle can be otherwise suitably configuredand/or arranged in relation to the aircraft.

The outer surface functions to separate the internal features andcomponents of the nacelle from the external airflow. The outer surfacecan also function to define at least a portion of the inlet and/oroutlet. The outer surface can also function to define the wetted surface(e.g., substantially all of the wetted surface, most of the wettedsurface, etc.) of the aircraft propulsion system aft of the rotor. Theouter surface can also function to define a geometry that minimizes drag(e.g., encourages laminar boundary layer formation and maintenance,prevents flow separation, etc.). The outer surface is preferably shapedto promote laminar flow, which can include: defining a cross sectionthat minimizes static pressure recovery along the surface in the axialdirection, which can lead to undesirable flow separation; acceleratingthe flow along a maximized downstream portion of the outer surface(e.g., maintaining a negative pressure gradient oriented along the outersurface direction) to promote laminar boundary layer stability; and/orany other suitable geometric features configured to promote laminar flowalong a maximal portion of the nacelle outer surface.

The lumen functions to define a volume that retains components of theaircraft propulsion system and/or other aircraft subsystems. Suchretained components can include, in variations, at least a portion of atilt mechanism, all or a portion of the power supply, power deliverysubsystems (e.g., electrical power distribution cables, conduits, etc.),mechanical actuators (e.g., for actuating control surfaces of theaircraft), all or a portion of the drive mechanism, and any othersuitable components.

The drag reduction portion functions to reduce drag on the aircraftpropulsion system, and thus on the aircraft as a whole, during flightoperations. The drag reduction portion is preferably configured toreduce drag during forward flight (e.g., operation of the aircraft inthe forward arrangement, operation of the aircraft propulsion system inthe forward configuration, etc.), but can additionally or alternativelyreduce drag during any suitable operating mode of the aircraft (e.g.,hover, vertical take-off and/or landing, forward motion of the aircraftwith at least a subset of aircraft propulsion systems of the aircraftbetween the forward and hover configurations, etc.). The drag reductionportion includes an inlet and an outlet; the drag reduction mechanismcan optionally include a diffuser and/or a bypass.

In some aspects, an aerial vehicle may use bladed propellers powered byelectric motors to provide thrust during take-off. The propeller/motorunits may be referred to as rotor assemblies. In some aspects, the wingsof the aerial vehicle may rotate, with the leading edges facing upwards,such that the propellers provide vertical thrust for take-off andlanding. In some aspects, the motor driven propeller units on the wingsmay themselves rotate relative to a fixed wing, such that the propellersprovide vertical thrust for take-off and landing. The rotation of themotor driven propeller units may allow for directional change of thrustby rotating both the propeller and the electric motor, thus notrequiring any gimbaling, or other method, of torque drive around orthrough a rotating joint.

In some aspects, aerial vehicles according to embodiments of the presentinvention take off from the ground with vertical thrust from rotorassemblies that have deployed into a vertical configuration. As theaerial vehicle begins to gain altitude, the rotor assemblies may beginto be tilted forward in order to begin forward acceleration. As theaerial vehicle gains forward speed, airflow over the wings results inlift, such that the rotors become unnecessary for maintaining altitudeusing vertical thrust. Once the aerial vehicle has reached sufficientforward speed, some or all of the blades used for providing verticalthrust during take-off may be stowed along their nacelles. In someaspects, all rotor assemblies used for vertical take-off and landing arealso used during forward flight. The nacelle supporting the rotorassemblies may have recesses such that the blades may nest into therecesses, greatly reducing the drag of the disengaged rotor assemblies.

After take-off, the aerial vehicle will begin a transition to forwardflight by articulating the rotors from a vertical thrust orientation toa position which includes a horizontal thrust element. As the aerialvehicle begins to move forward with speed, lift will be generated by thewings, thus requiring less vertical thrust form the rotors. As therotors are articulated further towards the forward flight, horizontalthrust, configuration, the aerial vehicle gains more speed.

The electric motor/propeller combination being on the outboard side ofthe articulating joint allows for a rigid mounting of the propeller tothe motor, which is maintained even as the propeller is moved throughvarious attitudes relative to the rear nacelle portion. With such aconfiguration the rotating power from the motor need not be gimbaled orotherwise transferred across a rotating joint. The deployment is of theentire motor driven rotor in some aspects.

In a first vertical configuration according to some embodiments of thepresent invention, as seen in a vertical take-off configuration in FIG.2A, an aerial vehicle 200 uses fixed wings 202, 203, which may beforward swept wings, with rotors of the same or different types adaptedfor both vertical take-off and landing and for forward flight. Theaircraft body 201 supports a left wing 202 and a right wing 203. Motordriven rotor assemblies 206, 207 on the wings include propellers whichmay stow and nest into the nacelle body. The aircraft body 201 extendsrearward is also attached to raised rear stabilizers 204. The rearstabilizers have rear rotor assemblies 205 attached thereto. Althoughtwo passenger seats are anticipated, other numbers of passengers may beaccommodated in differing embodiments of the present invention.

In some aspects, all or a portion of the wing mounted rotors may beadapted to be used in a forward flight configuration, while other wingmounted rotors may be adapted to be fully stowed during regular,forward, flight. The aerial vehicle 200 may have four rotors on theright wing 203 and four rotors on the left wing 202. The inboard rotorassemblies on each wing may have wing mounted rotors 206 that areadapted to flip up into a deployed position for vertical take-off andlanding, to be moved back towards a stowed position during transition toforward flight, and then to have their blades stowed, and nested, duringforward flight. The outboard rotor assembly 207 may pivot in unison froma horizontal to a vertical thrust configuration.

Similarly, the each rear stabilizer 204 may be have rotor units mountedto it, both of which are adapted to be used during vertical take-off andlanding, and transition, modes. In some aspects, all of the rotordesigns are the same, with a subset used with their main blades forforward flight. In some aspects, all of the rotor designs are the same,with all rotors used for forward flight. In some aspects, there may be adifferent number of rotor units mounted to the rear stabilizer 204.

In some embodiments, the electric motors of the aerial vehicle arepowered by rechargeable batteries. The use of multiple batteries drivingone or more power busses enhances reliability, in the case of a singlebattery failure. In some embodiments, the batteries may be spread outalong the rotating portion, and there may be one battery for each of themotor/ducted fan assemblies. In some embodiments, the battery orbatteries may reside in part or fully within the aircraft body, withpower routed out to the motors through the rotational couplings. In someembodiments, the batteries reside within the vehicle body on a rack withadjustable position such that the vehicle balance may be adjusteddepending upon the weight of the pilot.

FIG. 2B illustrates the aerial vehicle 200 in a forward flightconfiguration.

FIG. 3A illustrates, in partial view, a nacelle 303 which providesaerodynamic cover for support structure for a motor driven rotorassembly according to some embodiments of the present invention. Aspinner, or cowling, 301 is mounted forward of the rotor 302 (propellernot shown in this view). FIGS. 3B is a drawing of a nacelle 303 showingthe rotor with some other portions omitted for clarity. In some aspects,the nacelle may be a multi-piece nacelle adapted to allow for theforward portion of the nacelle to transition from a forward facinghorizontal configuration to a vertical take-off and landingconfiguration with the use of an internally mounted deploymentmechanism. In some aspects, the nacelle may be a wingtip mounted nacellewhich is adapted to transition between a horizontal and vertical flightconfiguration by rotating around a central pivot hub.

The rotor 302 rotates around an internal stator. An air gap 304 betweenthe external surface of the rotor 302 and the nacelle 303 allows for theinletting of air into the inside of the nacelle. In some aspects, theexternal circumferential surface of the nacelle 302 will also have airinlets which allow for the routing of air into the inner area of therotor structure. In some aspects, the external rotor structure hasexterior face skin surfaces with a lattice work of interior supportbetween the face skin surfaces, which allow for the flow of air andcooling of the structure using the flow of this air. The air flowingthrough this rotor structure exits out of the structure in an areaadjacent to the inflow air through the air gap 304. These airflows arethen available to flow through heat exchangers which cool liquid whichhas flowed through the internal stator of the motor. In some aspects,the external rotor structure will not allow for airflow within theexternal rotor structure. The air flow inletted through the air gap 304may work to lower drag of the aerial vehicle.

FIGS. 3C and 3D are drawings of the rear portion of a nacelle 303. Arear airflow exit 305 allows for the exit of the inflow air which hasentered the nacelle through the air gap 304 and through the rotorstructure. In some aspects, the nacelle 303 may be a split nacelle withan interior deployment mechanism, which may split as the nacelle andmotor driven assembly transition from a forward flight configuration toa vertical take-off and landing configuration. Once the nacelle issplit, the air exiting from the motor area may exit through the gapcreating in splitting the nacelle. In some aspects, the nacelle may be asolid nacelle, and the transition from a forward flight configuration toa vertical take-off and landing configuration involves rotating theentire nacelle around a fixed pivot. In some aspects, an aerial vehiclemay have a combination of motor driven rotor assemblies, some of whichhave splitting nacelle and some rotating around a fixed pivot. In someaspects, as discussed below, there may be one or more additionaloutlets.

FIGS. 4A, 4B, 4C, 5A, and 5B illustrate a rotor assembly 205 accordingto some embodiments of the present invention. In this illustrativeembodiment, the propeller and cowling are coupled to the rotatingstructure 302 and reside forward of the nacelle 303. Air is able toenter into heat exchangers 319 in area forward of the nacelle 303 andrearward of the rotor. In some aspects, the front rim of the nacelle 303defines an air gap 304 which allows air flow into the nacelle. In thisembodiment, all of the air that flows into the interior of the nacelleflows through heat exchangers 319 before exiting via the airflow exit305. A blocking structure 402 at the back end of the heat exchanger airflow openings blocks air from flowing further rearward into the nacellepast the heat exchanger. Although the blocking structure is illustratedwith some oval openings in FIG. 4C, for example, it is anticipated thatthese openings will provide access for items such as electrical wiringand will be otherwise impervious to airflow when in use. Air flows intothe heat exchangers 319 and then into the inside of the interiorstructure 404 within the nacelle. The airflow may then exit the insideof the interior structure 404 through vent holes 405, and then flowwithin the nacelle 303 and out the airflow exit 305. A deploymentmechanism 403 is adapted to pivot the rotor assembly from a forwardflight configuration to a vertical take-off and landing configuration.The support structure 411 supports the heat exchangers and also allowsairflow that has flowed through the heat exchangers to enter then intothe interior structure 404 of the nacelle.

FIGS. 6A, 6B, 7A, and 7B illustrate an embodiment of a rotor assembly207 wherein the airflow may flow through the heat exchangers and thenflow out through a main airflow exit 501, but may also allow a bypassstream to flow past the inlets of the heat exchangers 319 and be routedout through a bypass exit 505. FIG. 6C illustrates the rotor assemblywith the outer nacelle surface removed for clarity of viewing. In thisillustrative embodiment, airflow enters through the ring gap 304. Aportion of the airflow may route past the entrance to the heatexchangers and into an area behind the heat exchangers where itsrearward flow is blocked by a bypass blocking structure 507. A bypassduct 506 is fluidically coupled to the area rearward of the heatexchangers and forward of the bypass blocking structure 507. The bypassduct allows the bypass stream to continue out to the bypass exit 505.The nacelle may be pivotable around a pivot 502 to transition from aforward flight configuration to a vertical take-off and landingconfiguration.

The addition of a bypass stream allows for a larger volume of air to beinletted through the ring gap than may be able to be used by, or thatwould be needed by, the thermal management subsystem. This ability toallow for a larger volume of air flow may allow the user to tune thedrag reduction portion to lower energy loss of the aircraft. Asdiscussed below, in some aspects the ratio of the volume flow rate ofthe inletted airflow relative to the volume flow rate of the boundarylayer forward of the inlet may be set in order to reduce drag. In someaspects, in order to allow for more inletted airflow, a bypass stream isutilized.

Another portion of the airflow into the ring gap 304 may enter the heatexchangers 319 and exit within the interior of an inner nacellestructure 504. The inner nacelle structure 504 may have airflow passages508 adapted to allow the air within the inner nacelle structure to exitthe interior of the inner nacelle structure and travel within theinterior of the nacelle 503. The air within this area of the nacelle maythen continue out of the nacelle through a main airflow exit 501.

FIG. 8 is a drawing of a motor and propeller hub, with some partsomitted for clarity. The propeller hub 310 is mounted to the rotor 302and rotates in unison with the rotor. The propeller hub has propellerinterfaces 311 spaced around its periphery.

In some embodiments of the present invention, as seen in cutaway view inFIGS. 9A, 9B, and 9C, aspects of the motor cooling system are displayed.In some aspects, the cooling system may have air cooling through therotor structure, and liquid cooling within the stator structure. Theliquid cooling system may use a heat exchanger which facilitates heattransfer from the liquid to airflow flowing through the vanes of theheat exchanger. The airflow through the rotor structure may also in partcool the fluid after exiting the rotor structure and then entering theheat exchanger. In addition, the cooling system may utilize a fan topromote further airflow. In some aspects, there is not air flow throughthe rotor structure.

The stator 342 is coupled to the inner race of a bearing. The rotor 343is coupled to the outer race. The rotor 343 has a rotor supportstructure 315 adapted to support various components, including magnets312. In an exemplary embodiment, the rotor support structure 315 mayhave metal face skins 360, 361 with an inner lattice structure 364adapted to both be structurally supportive of the mechanical loads placeon the rotor support structure while also allowing air to flow throughthe structure to cool the structure. Air may enter into the rotorsupport structure through voids 362 in a face skin 360. In some aspects,the air entry voids may be around the front of the outer periphery ofthe rotor support structure. The airflow through the rotor supportstructure may exit through the rear 363 of the structure.

The stator 342 may have structure adapted for internal flow, such as theportion 314 under the stator winding bars 313. There may be a fluidcapture cover, such as a fiberglass cylindrical portion, around theouter circumference of the stator winding bars. The fluid capture coverallows for fluid to flow between the stator winding bars to allow forconvective cooling of the stator winding bars and windings. Within thestator is a fluid flow structure 316 which routes fluid from the fluidpump 317, through the fluid flow structure 316, forward through thestator support structure 314, back around through the stator windingbars 313 and under the fluid capture cover, and through heat exchangers319.

Air flow through the heat exchangers may be a combination of air exitingthe rear of the rotor support structure 315 and other air inlettingthrough the air gap 304 between the external surface of the rotor 302and the nacelle 303. In some aspects, there is a solid rotor supportstructure, wherein the airflow into the heat exchangers does not travelthrough the rotor structure. After flowing through the heat exchanger319 the fluid then routes back through the fluid flow structure 316 tothe fluid pump 317. An air fan 318 also facilitates airflow through theheat exchangers 319. Although shown in expanded view in FIG. 9A, the airfan 318 may be coupled to the fan 318. In some aspects, the fluid pump317 may be driven by a motor to drive fluid through the fluid system. Insome aspects, the air fan 318 may be driven by a motor to pull airthrough the heat exchangers. In some aspects, the same motor may driveboth the air fan and the fluid pump. In some aspects, inletted airflowing through the heat exchangers may then drive the fan, which inturn drives the fluid pump.

FIGS. 10A and 10B are photographs of an exemplary portion of a rotorsupport structure according to some embodiments of the presentinvention. As seen in side view in FIG. 12, and as seen in FIGS. 10C and10D,the rotor support structure has a top solid surface and bottom solidsurface with a lattice work support structure in between. In someaspects, the rotor support structure may be unitary piece constructedusing 3D printing of metal. As seen in FIG. 10D, a series of voids inthe outer circumference of the top solid surface allow for airflow entryinto the interior lattice work. The airflow is then able to exit theinterior lattice work of the rotor support structure via the outersurface of the rotor support structure.

FIG. 11 illustrates air and fluid flow through a liquid cooled electricmotor according to some embodiments of the present invention. FIG. 11 isa cutaway view with the pump 317 and the fan 318 in exploded viewpositions for clarity. In an exemplary embodiment, fluid resides withinin the fluid flow structure 316 and flows from the pump 317 and flowsradially outward 334 within outflow passages within the fluid flowstructure 316, which may be part of or coupled to the stator supportstructure. Heat generating electrical components may be mounted ontoforward side of the fluid flow structure and the fluid within the fluidflow structure may cool those components. The fluid then flows 332within the stator support structure 314 in an area adjacent to andradially inward from the winding bars and windings. The fluid then exitsthe interior of the stator support structure 314 at the front of thestator support structure and then routes rearward 336 through thewinding bars 313 and windings and radially within the fluid capturecover. The fluid then flows 337 through the heat exchangers 319 where itis cooled by airflow through the heat exchanger. Finally, the fluidflows 338 through return passages within the fluid flow structure andinto the pump 317.

Airflow through the motor enters through a path 331 through the rotorsupport structure 315. Some or all of the airflow exiting the rotorsupport structure may also then enter into the heat exchangers 319.Airflow also flows 330 around the exterior of the rotor and flows down333 through the heat exchangers 319. Both the external airflow 330 andthe internal airflow 331 may enter through the airflow gap 304. In thecase of a solid rotor no air will flow through the rotor supportstructure. The air fan 318 may also draw air in and through the airflowsystem described above. In some aspects, the air fan may be used to drawin a significant amount of air in order to have a beneficial influenceaircraft aerodynamics. In some aspects, such as in hover mode, the airfan may be the primary driver for air flow through the heat exchangers.The relatively narrow gap between the motor and nacelle is used toingest the boundary layer formed on the motor, which helps to clean upthe boundary layer flow on the nacelle itself, promoting laminar flow onthe nacelle and therefore reducing drag. In some aspects, the nacelle isshaped to take advantage of this beneficial influence. In someembodiments, there is no flow airflow through the rotor structure. Insuch embodiments, all airflow into the heat exchangers, or into thebypass ducts, is the external airflow 330.

In an exemplary embodiment, the coolant pump may be pumping in the rangeof 10-15 liters per minute of coolant, which may be a polyalphaolefincoolant. The coolant temperature entering the heat exchanger may beapproximately 85 C and upon exit may be 70 C. This may occur with themotor running at a continuous hover power of 75.5 kW and 1030 Nm torquewhile running at 700 rpm. The motor may reject 6.3 kW of heat in thisscenario. The fan airflow may vary between 800-1500 cfm.

The flow moderator 181 can be arranged in various positions relative tothe bypass duct 183 and may be used to moderate or direct the flow orflow volume of the inletted air. The inletted air may enter through theinlet 180 and a portion of the airflow may bypass the heat exchanger 184and enter the bypass duct 183. The fan 182 may be used to enhance theairflow volume. In some aspects, a flow moderator is used to change theproportion of flow volume which enters the bypass duct. In some aspects,an actuated system may engage mechanical flow directors, such aslouvers, which can alter the flow volume into the bypass duct 183. Insome aspects, the flow moderator may also alter the total amount of airinletted through the air inlet 180.

In some embodiments of the present invention, as seen in FIG. 13, amulti-channel diffuser 196 is used to slow the inletted air 191 as itenters a bypass duct 195 in a system with a rotor rotating around anaxis 197. The multi-channel diffuser 196 may reside within the nacelle194 adjacent to or behind the air inlet and in the fore area of thebypass duct 195. In this exemplary embodiment, all of the inletted air191 from the flowing air 190 flows through the diffuser and intoducting. In some aspects, the multi-channel diffuser may be used in theinletted airstream that then splits between entry into a thermal controlsystem and a bypass duct. In some aspects, the multi-channel diffusermay be used in an inletted airstream which wholly through a thermalcontrol system.

FIG. 14 illustrates an advantage of the multi-channel diffuser relativeto a single channel flow path. In the single channel flow path, inlettedair 260 may separate 261 from the internal surfaces of the channel asthe channel expands in volume. In a multi-channel diffuser, the airflows 270 a, 270 b, 270 c through channels separated by diffuser layers271 a, 271 b. The air 271 a, 271 b, 271 c exiting from the channelswithin the multi-channel diffuser has not separated from the internalsurfaces of the channel.

In a variation, as shown in FIG. 15A, the airflow path can flow into asegmented fan 180. The segmented fan 180 is preferably configured tocorrespond to a segmented diffuser of the nacelle, as seen in FIG. 15B,but can be otherwise suitably configured. In this variation, thesegmented fan 180 can function to extract momentum from the flow at afirst segment 181 (e.g., an outer segment of concentric segments) andsupply momentum to the flow at a second segment 183 (e.g., an innersegment of concentric segments). The segmented fan 180 may include aseparator 182, such as a cylindrical separator. In an exemplary case,inletted air 185 a, 185 b may travel on different sides of a diffuserplate 189. The diffuser plate 189 may begin on the outboard side of theheat exchanger 188 at the forward area of the nacelle 186. The diffuserplate concentrically separates the flow into the two airflow paths 185a, 185 b. The channelized airflow provided by the diffuser plates maycontinue through the heat exchanger and into the interior of thenacelle.

In some embodiments of the present invention, as seen in FIG. 15C, amulti-channel diffuser has a plurality diffuser plates 189 a, 189 b, 189c, 189 d, 189 e, 189 f, 189 g. The diffuser plates may begin on theoutboard side of the heat exchanger 188 at the forward area of thenacelle 186. The diffuser plate concentrically separates the flow intothe different airflow paths. The channelized airflow provided by thediffuser plates may continue through the heat exchanger and into theinterior of the nacelle. In some aspects, the diffuser plate structuresalso act as turning vanes for the airflow. It should be noted that afunction of the channelizing diffuser is to separate areas of the airflow that have different total pressure. A function of the diffuser isto slow the flow and increase its pressure inside the nacelle.

The drag reduction portion preferably functions to reduce drag bypromoting laminar flow over at least a portion of the outer surface ofthe nacelle, which is physically promoted by ingesting the boundarylayer (e.g., a turbulent boundary layer) at the location between therotor and the nacelle (e.g., the location where the boundary layer ismost likely to be fully turbulent downstream of the rotor due tophysical structural separation between the rotor and nacelle). Afteringestion (e.g., via the inlet/air gap), the internal airflow ispreferably expanded (e.g., via the diffuser) and decelerated such thatthe skin friction between the internal airflow and the drag reductionmechanism is reduced (e.g., proportionally to flow velocity reduction).This can result in a net drag reduction, in combination with themaintenance of laminar flow along the outer surface downstream of theinlet (e.g., and concomitant reduction in skin friction in comparisonwith a turbulent flow). The drag reduction portion also preferablyminimizes internal pressure losses (e.g., in the diffuser, in thecoupled heat exchanger, etc.). However, the drag reduction portion canadditionally or alternatively reduce drag in any other suitable manner.

In variations, the drag reduction portion can be operated betweenvarious modes, including a full bypass mode, a partial bypass mode, anda no-bypass mode. In the full bypass mode, the flow through the dragreduction portion is not driven through the heat exchanger of thethermal management subsystem (e.g., the flow bypasses the heatexchanger). In the no-bypass mode, the entirety of the flow through thedrag reduction portion is driven through the heat exchanger of thethermal management subsystem. In the partial bypass mode, the bypassfraction (e.g., the percentage of the flow through the drag reductionmechanism that bypasses the heat exchanger) is modulated. The partialbypass mode can function to manage possible pressure losses in the heatexchanger that can result from operating in the no-bypass mode atcertain aircraft speeds; in such cases, the partial bypass mode can beutilized to direct a fraction of the ingested air between the inlet andoutlet without passing the air through the heat exchanger to prevent toomuch airflow from being supplied to the heat exchanger (e.g., andcausing pressure losses or other drag-inducing and/or efficiencyreducing losses). The bypass fraction can be passively modulated (e.g.,actuated by the flow field itself, as a function of flow velocity)and/or actively modulated (e.g., throttled by a controllable flowactuator such as a variable-size orifice, valve, etc.). The dragreduction portion is preferably operated between the operating modesusing a bypass mechanism such as louvers which are driven by anelectromechanical actuator that can redirect the airflow through thedrag reduction portion and/or away from the drag portion mechanism, asshown by example in FIG. 12; however, the drag reduction portion canadditionally or alternatively be otherwise suitable transitioned betweenthe various operating modes and any other suitable operating modes.

In variations, the drag reduction portion can be passively operated. Inan example of this variation, the components of the drag reductionportion are preferably static (e.g., the inlet size is fixed, thediffuser shape and size is fixed, the outlet size is fixed, etc.), andthe airflow through the drag reduction portion can scale with thevelocity of the system (e.g., the airspeed of the aircraft). In anotherexample of this variation, the components of the drag reduction portioncan be dynamically actuated by the flow field (e.g., wherein thepressure of the flow field applies a force to the outlet and increasesor decreases the size of the outlet as a function of airspeed). However,the drag reduction portion can additionally or alternatively bepassively operated in any suitable manner, and/or actively operated(e.g., by an actuatable variable-sized outlet, etc.).

The inlet of the drag reduction portion functions to ingest the airflowthat moves passed the trailing edge of the cowling of the rotor. Theinlet is preferably shaped to minimize and/or prevent flow separation,to promote laminar flow on the outer surface of the nacelle downstreamof the inlet. However, the inlet can be otherwise suitably shaped. Thedrag reduction portion can be designed such that the amount of airingested at a design airspeed has been tuned such that drag isminimized.

The inlet is preferably arranged proximal the separation region (e.g.,gap) between the rotating external surface of the rotor system (e.g.,the rotor) and the static external surface of the rotor system (e.g.,the outer surface of the nacelle). In particular, the inlet ispreferably arranged proximal the location at which the flow downstreamof the rotor would stagnate on the rotor system in the absence of aninlet, to leverage the high-pressure zone resulting from the stagnationto drive airflow into the inlet (e.g., in addition to or alternativelyto active flow actuation such as via a flow actuator or large negativepressure gradients between the outlet and the inlet). The inlet ispreferably an annular region, but can additionally or alternatively be apartial annulus, a segmented annulus, and/or have any other suitablegeometric configuration.

The outlet functions to reintroduce the internal airflow (e.g., from thediffuser) to the external freestream. The outlet can also function torestrict the flow rate through the drag reduction mechanism (e.g.,passively via the outlet geometry, actively via actuation of the outletsize, etc.). The outlet can be arranged at various locations withrespect to the outer surface of the nacelle. The outlet can be arrangedat the outer surface, aft of the inlet, and upstream of the trailingedge or region of the nacelle. In an alternative variation, the outletcan be arranged at the trailing edge or region of the nacelle (e.g., inthe wake of the nacelle). The outlet can be an annular region (e.g., ina similar manner as the inlet), a segmented annular region, a regionlocated proximal to the inlet to minimize the impact of outflow throughthe outlet on downstream airflow, and/or have any other suitablegeometric distribution or arrangement with respect to the nacellegeometry.

The outlet can be of fixed or variable geometry (e.g., cross-sectionalsize, diameter, shape, etc.). In variations wherein the outlet is ofvariable size, the size can be manually varied (e.g., via a controllinkage, via a manually adjustable mechanical restrictor such as an irisor other orifice, via a fly-by-wire actuator, etc.) or automaticallyvaried (e.g., via a closed loop controller, via a speed-dependentvariable throttle, etc.).

FIG. 16A is a velocity magnitude modeling output for the velocity ofairflow through a diffuser 289 as it enters into the interior of anacelle 286. The airflow flows past the exterior surface of the rotor291 and enters into an air gap between the rotor 291 and the nacelle286. The diffuser 289 is a multi-channel diffuser with a plurality ofdiffuser plates. As illustrated in FIG. 16A, the velocity of the airflowhas slowed in the diffuser and through the nacelle. As seen in thepressure distribution modeling output of FIG. 16B, an increased pressureis seen just outboard of the diffuser, and throughout the diffuser andnacelle. As seen in FIG. 16B, the use of a multi-channel diffuser with aplurality of diffuser plates segregates higher pressure to the channelsaxially rearward, preventing recirculation of air in the overall flowchannel. At the rearward end of the diffuser plates a fan works to eventhe pressure rearward of the fan by momentum transfer, as discussedabove. The pressure differences within the diffuser channels are afraction of the external flow dynamic pressure. In some aspects, thepressure differences within the diffuser channel are in the range of 5%to 100% of the external dynamic pressure. In some aspects, the pressuredifferences within the diffuser channel are in the range of 10% to 50%of the external dynamic pressure.

A design parameter for the design and tuning of the drag reductionportion of systems according to some embodiments of the presentinvention is the volume flow fraction. The volume flow fraction isdefined as the ratio of the volume flow rate of the inletted air to thevolume flow rate of the boundary layer at the rear of the rotor andforward of the inlet. FIG. 20 illustrates the energy loss 270 vs. thevolume flow ratio 271. The horizontal axis 271 is set at the level ofenergy loss seen in a baseline system without ingestion of inletted air.As seen, as air is inletted the energy loss goes up 272 due to internallosses. As more air is inletted, a point is reached where the energylosses go down 273. This is due to restoral of laminar flow on theexternal surface of the nacelle, as seen in FIG. 19A. A low energy losspoint 274 may be reached that represent less energy loss than thebaseline system without ingestion of inletted air. With even moreinletted air, the internal losses rise and the overall energy lossincreases 275. In some aspects, the volume flow fraction is greater than0.1. In some aspects, the volume flow fraction is greater than 0.2. Insome aspects, the volume flow fraction is greater than 0.5. In someaspects, the volume flow fraction is greater than 1.0. In some aspects,the volume flow fraction is greater than 2.0.

A method for the reduction of energy losses of an aircraft may comprisethe steps of ingesting air in an area rearward of the rotor, routing theair into a diffuser, and outletting the air. The diffuser may route allor part of the ingested air through a thermal management system. Abypass pass duct may be utilized to increase the volume flow rate ofingested air.

FIGS. 17A, 18A, and 19A illustrate the turbulent intensity at 0%, 10%,and 20% suction velocity fractions, respectively. The turbulentintensity is the fraction of turbulent energy fluctuations in freestreamrelative to flow energy density. The brighter area indicates moreturbulent flow. The suction velocity fraction represents the suctionvelocity fraction of freestream. At 0% suction velocity fraction, asseen in FIG. 17A, the spinner 401 is relatively free of a turbulentboundary layer. As the flow approaches the air gap inlet 402, turbulencebegins. In this example there is no suction velocity at the air gapinlet 402. A turbulent layer 403 is seen all along the nacelle 404. At10% suction velocity fraction, as seen in FIG. 18A, the spinner 401 isrelatively free of a turbulent boundary layer. As the flow approachesthe air gap inlet 402, turbulence begins. In this example there is 10%suction velocity fraction at the air gap inlet 402. A thinning of theturbulent layer 405 is seen all along the nacelle 404 just after the airgap inlet 402. The turbulent layer later thickens downstream 406. At 20%suction velocity fraction, as seen in FIG. 19A, the spinner 401 isrelatively free of a turbulent boundary layer. As the flow approachesthe air gap inlet 402, turbulence begins. In this example there is 20%suction velocity fraction at the air gap inlet 402. A significantthinning 407, if not elimination, of the turbulent layer 405 is seen allalong the nacelle 404 just after the air gap inlet 402. The turbulentlayer then begins 408 and later thickens downstream 406.

FIGS. 17B, 18B, and 19C illustrate the velocity at 0%, 10%, and 20%suction velocity fractions, respectively. These results illustrate thatthe flow picture outside the nacelle does not chamber much with thechange in suction velocity fraction.

In some embodiments, an aircraft may draw in air actively to cause, orcause to increase, the suction velocity at the air gap inlet. In someaspects, air may be drawn in actively in order to cool the electricmotor, as described above. In some aspects, air may be drawn in activelyregardless of whether that air is used specifically for motor cooling.

As seen, the quality of the flow on the nacelle drastically changesbetween 10% and 20% suction. In some aspects, the suction velocityfraction is greater than 10%. In some aspects, the suction velocityfraction is greater than 15%. In some aspects, the suction velocityfraction is greater than 20%.

As evident from the above description, a wide variety of embodiments maybe configured from the description given herein and additionaladvantages and modifications will readily occur to those skilled in theart. The invention in its broader aspects is, therefore, not limited tothe specific details and illustrative examples shown and described.Accordingly, departures from such details may be made without departingfrom the spirit or scope of the applicant's general invention.

What is claimed is:
 1. An aerial vehicle with a drag reduction system,said aerial vehicle comprising: a motor driven rotor assembly, saidmotor driven rotor assembly comprising: a rotor; a stator, said rotorrotationally coupled to said stator; a nacelle, said nacelle comprisinga nacelle structure coupled to said motor driven rotor assembly, saidnacelle defining an outer surface, the forward edge of said outersurface of said nacelle defining an air inlet gap behind said rotor,said air inlet gap fluidically coupled to an interior of said nacelle.2. The aerial vehicle of claim 1 wherein said motor driven rotorassembly further comprises a diffuser, said diffuser fluidically coupledto said air inlet gap, said diffuser fluidically coupled to saidinterior of said nacelle.
 3. The aerial vehicle of claim 1 wherein saidair inlet gap comprises a ring gap behind the outer periphery of saidrotor.
 4. The aerial vehicle of claim 2 wherein said air inlet gapcomprises a ring gap behind the outer periphery of said rotor.
 5. Theaerial vehicle of claim 1 wherein said nacelle comprises an airflowexit, said airflow exit fluidically coupled to an interior of saidnacelle.
 6. The aerial vehicle of claim 2 wherein said nacelle comprisesan airflow exit, said airflow exit fluidically coupled to an interior ofsaid nacelle.
 7. The aerial vehicle of claim 4 wherein said nacellecomprises an airflow exit, said airflow exit fluidically coupled to aninterior of said nacelle.
 8. The aerial vehicle of claim 1 wherein motordriven rotor assembly further comprises one or more annular ring heatexchangers, said one or more annular heat exchangers fluidically coupledto said air inlet gap on a first side, said one or more annular heatexchangers fluidically coupled to said interior of said nacelle on asecond side.
 9. The aerial vehicle of claim 7 wherein motor driven rotorassembly further comprises one or more annular ring heat exchangers,said one or more annular heat exchangers fluidically coupled to said airinlet gap on a first side, said one or more annular heat exchangersfluidically coupled to said interior of said nacelle on a second side.10. The aerial vehicle of claim 1 wherein motor driven rotor assemblyfurther comprises an air intake fan, said air intake fan adapted to suckair into said air gap, said air intake fan structurally coupled to saidstator.
 11. The aerial vehicle of claim 2 wherein motor driven rotorassembly further comprises an air intake fan, said air intake fanadapted to suck air into said air gap, said air intake fan structurallycoupled to said stator.
 12. The aerial vehicle of claim 9 wherein motordriven rotor assembly further comprises an air intake fan, said airintake fan adapted to suck air into said air gap, said air intake fanstructurally coupled to said stator.
 13. The aerial vehicle of claim 1wherein said motor driven rotor assembly is adapted to ingest air duringflight into said air gap at a flow volume ratio of greater than 0.2. 14.The aerial vehicle of claim 2 wherein said motor driven rotor assemblyis adapted to ingest air during flight into said air gap at a flowvolume ratio of greater than 0.2.
 15. The aerial vehicle of claim 2wherein said motor driven rotor assembly is adapted to ingest air duringflight into said air gap at a flow volume ratio of greater than 0.5. 16.The aerial vehicle of claim 11 wherein said motor driven rotor assemblyfurther comprises: a segmented fan, said segmented fan adapted totransfer momentum of a first portion of the airflow through said fan toa second portion of the airflow through said fan; and air flow channelstructures adapted to channelize the airflow through said diffuser intodifferent intake areas of said segmented fan.
 17. The aerial vehicle ofclaim 9 wherein motor driven rotor assembly further comprises: a bypassduct, said bypass duct fluidically coupled to said air inlet gap; and abypass airflow exit.
 18. The aerial vehicle of claim 17 wherein saidmotor driven rotor assembly is adapted to ingest air during flight intosaid air gap at a flow volume ratio of greater than 0.2.
 19. The aerialvehicle of claim 17 wherein said motor driven rotor assembly is adaptedto ingest air during flight into said air gap at a flow volume ratio ofgreater than 0.5.
 20. The aerial vehicle of claim 17 wherein said motordriven rotor assembly is adapted to ingest air during flight into saidair gap at a flow volume ratio of greater than 1.0.